Secret-key single-message authentication: Crypto.Saltine.Core.OneTimeAuth

The auth function authenticates a message ByteString using a secret key The function returns an authenticator. The verify function checks if it's passed a correct authenticator of a message under the given secret key.

The auth function, viewed as a function of the message for a uniform random key, is designed to meet the standard notion of unforgeability after a single message. After the sender authenticates one message, an attacker cannot find authenticators for any other messages.

The sender must not use auth to authenticate more than one message under the same key. Authenticators for two messages under the same key should be expected to reveal enough information to allow forgeries of authenticators on other messages.

Crypto.Saltine.Core.OneTimeAuth is crypto_onetimeauth_poly1305, an authenticator specified in "Cryptography in NaCl" (http://nacl.cr.yp.to/valid.html), Section 9. This authenticator is proven to meet the standard notion of unforgeability after a single message.

This is version 2010.08.30 of the onetimeauth.html web page.